Increased efficiency fractional distillation tray

#1. Field of the Invention

#The invention relates to an apparatus for increasing the efficiency of fractional distillation trays. The invention more specifically relates to a process and apparatus providing a higher efficiency multiple downcomer fractionation tray.

#2. Related Art

#The working of the invention and the typical arrangement and variations in parts of the apparatus will be described through use of the accompanying drawings in which:

#FIG. 1 illustrates the liquid flow downward from an upper first tray 1 onto the liquid distribution pan 7 and then onto the decking of the lower tray 2.

#FIGS. 2, 3, 4 and 5 illustrates two of the many possible different structural embodiments of the liquid distribution pans 7 of FIG. 1.

#Fractionation trays are employed to perform an almost endless variety of separations in the petroleum and petrochemical industries. Fractionation trays are used, for example, in the separation of many different hydrocarbons such as paraffins, aromatics and olefins. Trays are used to separate specific compounds such as alcohols, ethers, alkylaromatics, monomers, solvents, inorganic compounds, etc. and in the separation of broad boiling mixtures such as petroleum derived fractions including naphtha. This great utility has led to the development of a wide variety to trays having differing advantages and disadvantages.

#One widely used type of tray is the multiple downcomer tray illustrated in the above cited references. Multiple downcomer trays have several distinguishing physical characteristics. For instance, a multiple downcomer tray does not have the receiving pan traditionally shown on cross-flow trays. This is the normally imperforate section of tray deck located below the bottom of a downcomer. This is the area of a cross flow tray that the liquid descending through the downcomer impacts before passing horizontally onto the perforated decking of the tray. In a conventional tray the receiving pan is normally located directly below the downcomer leading from the next above fractionation tray. This differs from a multiple downcomer tray in which the horizontal surface area of the tray is divided only into areas functioning as downcomer means and flat vapor-liquid contacting area normally referred to as decking. There are no imperforate areas allocated to receiving descending liquid from the tray located immediately above.

#Another distinguishing feature of a multiple downcomer type fractionation tray is the provision of a relatively large number of parallel downcomers at equal distances across the tray. Each tray can employ from one to fifteen or more such downcomers, which are of similar design. These downcomers are spaced relatively close together compared to those of the more common crossflow fractionation trays as the downcomers are spread across the surface of the tray rather than being mainly at the periphery of the tray. The distance between adjacent downcomers (measured between their side walls) of the same multiple downcomer tray will be between 0.2 and 1.0 meters and preferably less than about 0.5 meter. This results in a tray having a unique design, when viewed from above, consisting of the alternating decking areas and downcomer means evenly spaced across the upper surface of the fractionation tray.